Conventional antiperspirants comprising salts of aluminum or aluminum/zirconium are known. These salts function as antiperspirants by forming polymeric complexes which can plug pores, thereby blocking sweat release. There is a need for additional antiperspirant active agents that provide complexes of a size capable of plugging pores to block sweat, that provide deodorant/antibacterial efficacy, and that are less irritating to the skin than the acidic salts in conventional antiperspirants. There is also a need for alternative antibacterial and skin protective agents for use in liquid hand soaps and body washes. Finally, there is a need for agents in oral care products which can whiten and strengthen teeth, retard erosion, and inhibit bacteria and plaque.
Certain zinc amino-acid complexes can produce zinc-containing precipitates upon dilution with water or other aqueous preparations. Some zinc-containing precipitates are composed of zinc oxide, zinc hydroxide, zinc halides, etc. The precipitates can be deposited onto skin as well as hard and soft dental tissues. Potential benefits related to deposition on the hard tissues include whitening, sensitivity relief, erosion protection and anticavity. Potential benefits related to deposition on the soft tissue include improvement in the host immune response, enhancement in the tissue's barrier function, etc. Zinc ions can be released from the depositions, providing antibacterial, bacteriostatic and other plaque and gingivitis benefits as commonly associated with zinc ions.
Some zinc amino-acid complexes, however, do not have the most optimal precipitation kinetics. In another words, their rate of precipitation upon dilution may be too slow or too fast for typical applications. For example, for oral care typical recommended brushing times range from 1 minute to 3 minutes, but an average person brushes for a significantly shorter duration. Typical recommended rinsing times with a mouthrinse is about a minute, but an average person spends much less time. Some zinc amino-acid complex dilutions typically require more than 3 minutes to precipitate in any substantial quantity, and the amount of precipitation is limited within a typical brushing and rinsing time.
Therefore, there exists a need for optimizing the precipitation times of zinc complexes. In particular, there is a need for reducing the precipitation times associated with the zinc amino-acid complexes with a slow precipitation profile.